rust: Add ref to generated sources (aidl, bindgen)

Test: SOONG_GEN_RUST_PROJECT=1 m nothing; Edit
  system/security/keystore2/selinux/src/lib.rs;
  Check name resolution in IDE.
Bug: 168263887
Change-Id: Icbbf176c4355c3043807ce3fe0c3967c4a1374e2

rust/project_json.go

@@ -75,6 +75,32 @@ func init() {
 	android.RegisterSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
 }
 
+// librarySource finds the main source file (.rs) for a crate.
+func librarySource(ctx android.SingletonContext, rModule *Module, rustLib *libraryDecorator) (string, bool) {
+	srcs := rustLib.baseCompiler.Properties.Srcs
+	if len(srcs) != 0 {
+		return path.Join(ctx.ModuleDir(rModule), srcs[0]), true
+	}
+	if !rustLib.source() {
+		return "", false
+	}
+	// It is a SourceProvider module. If this module is host only, uses the variation for the host.
+	// Otherwise, use the variation for the primary target.
+	switch rModule.hod {
+	case android.HostSupported:
+	case android.HostSupportedNoCross:
+		if rModule.Target().String() != ctx.Config().BuildOSTarget.String() {
+			return "", false
+		}
+	default:
+		if rModule.Target().String() != ctx.Config().Targets[android.Android][0].String() {
+			return "", false
+		}
+	}
+	src := rustLib.sourceProvider.Srcs()[0]
+	return src.String(), true
+}
+
 func (singleton *projectGeneratorSingleton) mergeDependencies(ctx android.SingletonContext,
 	module android.Module, crate *rustProjectCrate, deps map[string]int) {
 
@@ -116,11 +142,11 @@ func (singleton *projectGeneratorSingleton) appendLibraryAndDeps(ctx android.Sin
 		return cInfo.ID, crateName, true
 	}
 	crate := rustProjectCrate{Deps: make([]rustProjectDep, 0), Cfgs: make([]string, 0)}
-	srcs := rustLib.baseCompiler.Properties.Srcs
-	if len(srcs) == 0 {
+	rootModule, ok := librarySource(ctx, rModule, rustLib)
+	if !ok {
 		return 0, "", false
 	}
-	crate.RootModule = path.Join(ctx.ModuleDir(rModule), srcs[0])
+	crate.RootModule = rootModule
 	crate.Edition = rustLib.baseCompiler.edition()
 
 	deps := make(map[string]int)

rust/project_json_test.go

@@ -18,6 +18,7 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"android/soong/android"
@@ -100,22 +101,50 @@ func TestProjectJsonBindGen(t *testing.T) {
 	rust_library {
 		name: "liba",
 		srcs: ["src/lib.rs"],
-		rlibs: ["libbindings"],
+		rlibs: ["libbindings1"],
 		crate_name: "a"
 	}
 	rust_bindgen {
-		name: "libbindings",
-		crate_name: "bindings",
-		source_stem: "bindings",
+		name: "libbindings1",
+		crate_name: "bindings1",
+		source_stem: "bindings1",
 		host_supported: true,
 		wrapper_src: "src/any.h",
 	}
+	rust_library_host {
+		name: "libb",
+		srcs: ["src/lib.rs"],
+		rustlibs: ["libbindings2"],
+		crate_name: "b"
+	}
+	rust_bindgen_host {
+		name: "libbindings2",
+		crate_name: "bindings2",
+		source_stem: "bindings2",
+		wrapper_src: "src/any.h",
+	}
 	` + GatherRequiredDepsForTest()
 	fs := map[string][]byte{
 		"src/lib.rs": nil,
 	}
 	jsonContent := testProjectJson(t, bp, fs)
-	validateJsonCrates(t, jsonContent)
+	crates := validateJsonCrates(t, jsonContent)
+	for _, c := range crates {
+		crate, ok := c.(map[string]interface{})
+		if !ok {
+			t.Fatalf("Unexpected type for crate: %v", c)
+		}
+		rootModule, ok := crate["root_module"].(string)
+		if !ok {
+			t.Fatalf("Unexpected type for root_module: %v", crate["root_module"])
+		}
+		if strings.Contains(rootModule, "libbindings1") && !strings.Contains(rootModule, "android_arm64") {
+			t.Errorf("The source for libbindings1 does not contain android_arm64, got %v", rootModule)
+		}
+		if strings.Contains(rootModule, "libbindings2") && !strings.Contains(rootModule, "linux_glibc") {
+			t.Errorf("The source for libbindings2 does not contain linux_glibc, got %v", rootModule)
+		}
+	}
 }
 
 func TestProjectJsonMultiVersion(t *testing.T) {

rust/testing.go

@@ -117,6 +117,7 @@ func CreateTestContext() *android.TestContext {
 	ctx.RegisterModuleType("rust_binary", RustBinaryFactory)
 	ctx.RegisterModuleType("rust_binary_host", RustBinaryHostFactory)
 	ctx.RegisterModuleType("rust_bindgen", RustBindgenFactory)
+	ctx.RegisterModuleType("rust_bindgen_host", RustBindgenHostFactory)
 	ctx.RegisterModuleType("rust_test", RustTestFactory)
 	ctx.RegisterModuleType("rust_test_host", RustTestHostFactory)
 	ctx.RegisterModuleType("rust_library", RustLibraryFactory)